Micro-optic film materials projecting synthetic images generally comprise (a) a light-transmitting polymeric substrate, (b) an arrangement of micro-sized image icons located on or within the polymeric substrate, and (c) an arrangement of focusing elements (e.g., microlenses). The image icon and focusing element arrangements are configured such that when the arrangement of image icons is viewed through the arrangement of focusing elements, one or more synthetic images are projected. These projected images may show a number of different optical effects. Material constructions capable of presenting such effects are described in U.S. Pat. No. 7,333,268 to Steenblik et al., U.S. Pat. No. 7,468,842 to Steenblik et al., U.S. Pat. No. 7,738,175 to Steenblik et al., U.S. Pat. No. 7,830,627 to Commander et al., U.S. Patent Application Publication No. 2009/0008923 to Kaule et al.; U.S. Patent Application Publication No. 2010/0177094 to Kaule et al.; U.S. Patent Application Publication No. 2010/0182221 to Kaule et al.; European Patent Application No. 08784548.3 (or European Publication No. 2162294) to Kaule et al.; and European Patent Application No. 08759342.2 (or European Publication No. 2164713) to Kaule.
These film materials may be used as security devices for authentication of banknotes, secure documents and products. For banknotes and secure documents, these materials are typically used in the form of a strip or thread and either partially embedded within the banknote or document, or applied to a surface thereof. For passports or other identification (ID) documents, these materials could be used as a full laminate or embedded as an anti-counterfeit feature in polycarbonate passports.
Secure documents made up of fused multilayer polymer film materials have become increasingly popular in recent years. Common forms of these secure documents include passport data pages and ID cards in which multiple layers of polycarbonate, polyethylene terephthalate (PET), glycol-modified polyethylene terephthalate (PETG), and other thermoplastic polymers have been fused together to form a secure, indivisible structure. Such products are often formed from a number of layers of a single type of polymer, such as polycarbonate, with some of the layers containing different polycarbonate compositions. Some of the different layer compositions include opaque layers and clear layers. The clear layers may either contain or be free of laser markable materials.
An object of the present invention is to increase the complexity and thus the counterfeit-resistance of these secure documents by incorporating laser markable or laser marked optical (e.g., micro-optic) film materials. The static 2D images laser marked on, within, or below these film materials help determine the authenticity of the documents (e.g., documents having financial value, identity documents, non-secure documents) and products that employ them. The inventive materials may also be used simply for brand enhancement purposes (e.g., as (or as part of) a product label) with the laser marked 2D image providing, for example, a company logo or other brand identifier.
Laser personalization is widely used as a means to add customized personalization data to secure documents at the point of issue. This personalization feature further protects a secure document being issued by a government or corporate entity by allowing the issuer to personalize the document with the intended recipient's personal information. By way of the present invention, this type of personalization feature has been incorporated onto, into, or below an optical film material suitable for use with secure documents thereby enhancing the security features of these documents. In the past, micro-optic systems capable of presenting synthetic images did not contain laser markable substrate materials. Also, to this point in time, laser markable products have not contained micro-optic systems capable of presenting synthetic images.
Laser marking micro-optic film materials has in the past been deemed impracticable (i.e., not capable of being put into practice) due to the risk of causing permanent damage to these materials. As is known to those skilled in the art, laser writing causes overheating and swelling of these film materials, which results in bubbling, separation, or delamination at interfaces within the structure, and/or permanent damage to the microlenses and/or micro-sized image icons, thus causing permanent distortion of the synthetic images.
The present inventors have developed a method for laser marking a device that embodies or comprises an optical film material without physically damaging the material or distorting the image(s) projected by the material.
In particular, the present invention provides a method for laser marking one or more static 2D images on or within a device that embodies or comprises an optical film material that projects at least one synthetically magnified image, the method comprising:                identifying one or more layers or interfaces within the optical film material that may be damaged by laser energy, or by heat and gas generated by laser absorption within a laser receptive layer (hereinafter referred to as “laser sensitive layer or interface”);        either positioning one or more layers markable by laser energy above the laser sensitive layer or interface (hereinafter referred to as “laser markable layer”), positioning one or more thermal spacer layers and one or more laser markable layers below the optical film material, the thermal spacer layer(s) being located between the optical film material and the one or more laser markable layers, modifying the laser sensitive interface to increase the bond strength and/or thermal resistance of the interface, or replacing the laser sensitive layer with a layer made from a material with a higher bond strength and/or a higher thermal resistance;        optionally, molding the layers together using heat and pressure to form a device that embodies the optical film material (e.g., a card or composite structure); and        exposing the device to laser energy so as to mark one or more static 2D images on or into the one or more laser markable layers.        
The term “above”, as used herein, is intended to mean a layer that is closer to a source of laser energy than another layer in the inventive device, while the term “below”, as used herein, is intended to mean a layer that is farther from the laser energy source than another layer in the inventive device.
The term “laser markable” or any variant thereof, as used herein, is intended to mean capable of physical or chemical modification induced or formed by a laser including, but not limited to, carbonizing, engraving, engraving with or without color change, engraving with surface carbonization, color change or internal blackening, laser marking by coating removal, ablation, bleaching, melting, swelling, and vaporization, and the like. The term “laser marked” or any variant thereof, as used herein, is intended to mean carrying or displaying any mark formed by a laser or laser-like device.
The present invention also provides a laser markable optical device, which comprises:                an optical film material that comprises one or more optionally encapsulated arrangements of focusing elements and one or more arrangements of image icons disposed on opposing sides of an optical spacer layer, at least a portion of the focusing elements forming at least one synthetically magnified image of at least a portion of the image icons; and        optionally, one or more layers located above and/or below the optical film material,        wherein at least one arrangement or layer within or layer above or below the optical film material is markable by laser energy, and        wherein static 2D images may be laser marked on or into the laser markable arrangement(s) or layer(s) without damaging the focusing elements or the image icons of the optical film material, and without causing bubbling, separation, or delamination at any interface within the device.        
In a first exemplary embodiment, the optical film material of the laser markable optical device has one or more layers located above and/or below the film material (hereinafter the inventive device in which the optical film material has layers located above and also below the film material is sometimes referred to as a “composite security structure”).
In one such embodiment, the laser markable device is made up of an optical film material that comprises an arrangement of encapsulated refractive focusing elements and an arrangement of image icons that are separated by an optical spacer layer, and one or more layers located above or above and below the optical film material, wherein one or more arrangements or layers located above the arrangement of image icons is a laser markable arrangement or layer.
In another such embodiment, the arrangement(s) of focusing elements is an arrangement of reflective focusing elements and one or more arrangements or layers located above the arrangement of reflective focusing elements is a laser markable arrangement or layer.
In yet another such embodiment, the laser markable device is made up of an optical film material, one or more underlying laser markable layers, and one or more thermal spacer layers positioned between the optical film material and the one or more underlying laser markable layers. In this embodiment, laser marking takes place through the optical film material.
In yet a further such embodiment, the laser markable device is made up of an optical film material that comprises an arrangement of focusing elements embedded within an adhesive material, one or more underlying laser markable layers, and an adhesive layer positioned between the optical film material and the one or more underlying laser markable layers. In this embodiment, laser marking takes place through the optical film material.
In a second exemplary embodiment, the optical film material of the laser markable optical device is a stand-alone film material that is not covered or embedded.
In exemplary “stand alone” embodiments, the laser markable device is made up of an optical film material that comprises an arrangement of refractive or reflective focusing elements and an arrangement of image icons that are separated by a laser markable layer that also functions as an optical spacer.
The present invention further provides a laser marked optical device that basically comprises an optical film material as described above, and optionally one or more layers located above and/or below the optical film material, wherein at least one arrangement or layer of the optical film material or at least one layer above or below the optical film material is a laser markable arrangement or layer, and wherein the laser markable arrangement(s) or layer(s) has one or more laser marked static 2D images thereon.
The present invention also provides sheet materials and base platforms that are made from or employ the inventive laser markable or laser marked optical device, as well as documents made from these materials. The term “documents”, as used herein designates documents of any kind having financial value, such as banknotes or currency, and the like, or identity documents, such as passports, ID cards, driving licenses, and the like, or other documents, such as tags and labels. The inventive optical system is also contemplated for use with consumer goods as well as bags or packaging used with consumer goods, such as potato chip bags.
Other features and advantages of the invention will be apparent to one of ordinary skill from the following detailed description and accompanying drawings.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. All publications, patent applications, patents and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.